import math

x1, y1, x2, y2 = map(float, raw_input().split())
print round(math.sqrt((x1 - x2)**2 + (y1 - y2)**2), 5 ) import math math x1, y1, x2, y2 = map(float, raw_input().split()) x1 map(float, raw_input().split()) map float raw_input().split() ().split () raw_input split y1 x2 y2 print round(math.sqrt((x1 - x2)**2 + (y1 - y2)**2), 5 ) round math.sqrt((x1 - x2)**2 + (y1 - y2)**2) math.sqrt math sqrt (x1 - x2)**2 + (y1 - y2)**2 (x1 - x2)**2 x1 - x2 x1 x2 2 (y1 - y2)**2 y1 - y2 y1 y2 2 5 x2, y2 = map(float, raw_input().split()) map(float, raw_input().split()) x2 x1, y1, x2, y2 = map(float, raw_input().split()) map(float, raw_input().split()) x1 y2 = map(float, raw_input().split()) map(float, raw_input().split()) y2 y1, x2, y2 = map(float, raw_input().split()) map(float, raw_input().split()) y1
import math

x1, y1, x2, y2 = map(float, raw_input().split())
print round(math.sqrt((x1 - x2)**2 + (y1 - y2)**2), 5 )